Hydrogen can be produced in many ways:
1. Using Steam Methane Reforming (SMR). Most of current hydrogen is produced this way (~ 90 mtpa) from fossil fuels. It has high CO2 emission footprint and called Grey Hydrogen (when produced from natural gas SMR
2. Using Steam Coal Gasification (SCG). Hydrogen is produced this way . It has high CO2 emission footprint and called Brown Hydrogen (when produced from natural coal)
3. Using Electrolysis. When electricity is to electroayzers is provided by renewables energy(solar PV or -Wind), its called Green Hydrogen.